Multiple choice

One inlet pipe fills an empty tank in 5 hours. A second inlet pipe fills the same tank in 3 hours. If both pipes are used together, how long will it take to fill 2/3 of the tank?

  1. 8/15 hr

  2. 3/4 hr

  3. 5/4 hr

  4. 15/8 hr

  5. 8/3 hr
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Pipe 1 fills 1/5 of the tank per hour, and pipe 2 fills 1/3 of the tank per hour. Together, they fill (1/5 + 1/3) = 8/15 of the tank per hour. To fill 2/3 of the tank, the time required is (2/3) / (8/15) = (2/3) * (15/8) = 5/4 hours.

AI explanation

By adding their individual rates, the combined hourly rate of both inlet pipes is 1/5 plus 1/3, which equals 8/15 of the tank per hour. To find the total time to fill 2/3 of the tank, divide the target fraction by this hourly rate. Dividing 2/3 by 8/15 gives 5/4 hours.

Keep practicing — related questions